With cargo loading completed on October 14, 1942, the SS John W. Brown departed New York on the 15th of October starting her maiden voyage; bound for the Persian Gulf, where she would unload her strategic cargo of tanks, planes, vehicles, food and munitions for delivery overland to the Soviet Union; aiding in the war against Nazism. Her 14,400-nautical mile (16,560-statute mile; 26,667-km) route was designed avoid areas where Axis forces posed the greatest threats to Allied shipping. She made the first leg of the voyage in convoy, steaming down from New York Harbor to Guantanamo Bay, Cuba [NG.314], where she joined another convoy for the trip across the Caribbean Sea from Guantanamo to the Panama Canal Zone [GZ.9].
After passing through the canal to reach the Pacific Ocean, she steamed alone down the western coast of South America; requiring two weeks to reach Cape Horn. She then made a 17-day independent crossing of the South Atlantic Ocean to Cape Town, South Africa, stopping for two days to refuel and reprovision. Back underway, she steamed northward alone through the western Indian Ocean along the east coast of Africa, and anchored in the Persian Gulf on December 25, 1942; two and one half months after leaving New York.
Ports in the Persian Gulf were overwhelmed by the amount of cargo arriving from Allied countries, and so the John W. Brown was forced to lie at anchor for one month before she could begin to unload at Abadan, Iran, where she dropped off the two P-40s and some of the tanks she carried late in January 1943. It took another month and a half before she could enter port at Khorramshahr, Iran, to unload the rest of her cargo in March, 1943.
On March 16, 1943, the John W. Brown sailed to return to the United States. She steamed south from the Persian Gulf [with Convoy PB.31] along the eastern coast of Africa to Cape Town, again calling there for two days [then joining Convoy CN.16] before making a two-week crossing of the South Atlantic to Bahia, Brazil, where she arrived on April 23, 1943. There she joined a convoy [ BT.11] to steam north to Paramaribo, Surinam; proceeded upriver to Paranam to load bauxite, then steamed to Port of Spain, Trinidad, to load more bauxite. Fully loaded in Trinidad, she joined [Convoy TAG.60] to steam to Guantanamo Bay and then [Convoy GN.60] for the final leg of her voyage to New York City; where she arrived on May 27, 1943 completing her nearly eight month maiden voyage.